When It Comes to Building New Wetlands, Scientists Still Can't Fool Mother Nature
Nadis, Steve, National Wildlife
William Mitsch's task wasn't easy. He had to convince Ohio State University officials of the wisdom of building a swamp on campus, practically in the middle of Columbus, Ohio. But the ecology professor ultimately prevailed, arguing that the experimental wetlands would be a pleasant spot, not a mosquito haven. More importantly, he said, the site could provide university researchers with insight into how marshlands work and whether it is possible to create and restore wetlands that perform like natural systems.
Today, the research park on the banks of the Olentangy River, with its 12 acres of marshes, provides habitat for more than 130 species of birds and other creatures such as muskrats, beavers and foxes. The so-called "Buckeye Swamp" is also now a source of pride for university officials, whose attitudes toward wetlands have changed dramatically in the four years since the first two marshes were built.
A similar change in attitude is occurring all across the country, as Americans learn more about the valuable role wetlands play in protecting water supplies from pollution, preventing flooding and sustaining wildlife. But can the nation ever reclaim a significant portion of the millions of acres of marshlands, bogs and potholes it has destroyed under programs that actively promoted wetlands drainage and development? Last February, President Clinton unveiled an initiative that calls for increasing U.S. wetlands by about 100,000 acres per year as of 2005.
"While that objective is certainly commendable, the fact remains that restored or newly created wetlands cannot effectively replace the natural wetlands that we continue to lose every year in this country," says Tony Turrini, a National Wildlife Federation attorney who specializes in wetlands issues. "Researchers cannot effectively replicate all of the functions or complicated plant systems found in natural wetlands." Many ecologists involved with marshland restoration and construction efforts agree.
Despite significant progress in the science of wetlands restoration, observes University of Wisconsin ecologist Joy Zedler, "the result of these efforts will probably not mimic some previous pristine conditions. Most of what gets constructed today are simpler types of wetlands. We're losing much more complicated systems that nobody knows how to create." To have a chance of succeeding, Zedler adds, experts must keep experimenting and learning from previous successes and failures.
The early returns from Ohio State University are encouraging. There, researchers built two marshes in 1994--one planted with typical marsh vegetation, the other left unplanted. After three years, Mitsch says, plant cover was essentially the same in both of the basins.
While there may be some advantage in introducing plants to newly constructed wetlands, he notes, the best strategy seems to be setting up the right hydrologic conditions, leaving the system open so that animals can move in and seeds can take hold, and then letting nature run its course. "We're still not smart enough to know exactly how nature works," he says. "That's why 'designer wetlands,' where you specify in advance exactly what kind of vegetation you want, are not practical on a big scale."
A restoration project in the Sweetwater Marsh National Wildlife Refuge near San Diego, California, may be a case in point. To offset the loss of marshland from the widening of Interstate 5, the California Department of Transportation (Caltrans) began in 1984 to excavate a marsh at Sweetwater to provide habitat for two endangered birds, the light-footed clapper rail and the least tern, and one endangered plant, bird's beak. Fourteen years later, the ambitious criteria have been met for both the tern and bird's beak, but not for the clapper rail.
The main problem is that cordgrass, intended to serve as nesting sites for the birds, failed to grow to the birds' preferred height of about three feet. …